5-ioso-2-pyrimidinone nucleoside

ABSTRACT

The nuceoside 1-(2-Deoxy- beta -D-ribofuranosyl)-5-(iodo)-2-pyrimidinone possesses a high level of antiviral activity and a low level of toxicity to the host cell making it an especially effective therapeutic agent for HSV-2.

CROSS-REFERENCE TO RELATED APPLICATION

This is a continuation-in-part of application Ser. No. 641,770, filedAug. 20, 1984, now U.S. Pat. No. 4,782,142 which is acontinuation-in-part of application Ser. No. 337,297, filed Jan. 5,1982, now U.S. Pat. No. 4,468,384.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to novel compounds for inhibiting the replicationof DNA viruses, and more particularly, relates to a compound forinhibiting the replication of DNA viruses which induce the formation ofthymidine kinase enzyme.

2. History of the Prior Art

Historically, viruses have been the causative agents of many diseases ofboth plants and animals including man. Diseases caused by viruses havebeen very difficult to control or cure by traditional methods. Many suchviral diseases have been, in the past, effectively controlled throughmass vaccination but even in modern times, effective agents to cureviral diseases, rather than prevent them, have been unavailable.

It has been recently discovered that certain substituted naturallyoccurring pyrimidinones are effective antiviral agents. Most of suchcompounds are 5-substituted pyrimidinones attached to a pentose sugargroup at the one position of the pyrimidinone ring. Examples of suchcompounds and their effects are discussed in "Molecular Basis forSerendipitous Development of Antiviral and Anticancer Aminonucleosides"by W. H. Prusoff et al; "Comparative Study of the Potency andSelectivity of Anti-Herpes Compounds" by DeClercq and "Strategy for theDevelopment of Selective Anti-Herpes Virus Agents Based on the UniqueProperties of Viral Induced Enzymes--Thymidine Kinase, DNase and DNAPolymerase". All of these articles appear in Volume 57 of a Symposium ofthe Federation of European Biochemical Societies, Antimetabolites inBiochemistry, Biology and Medicine edited by Skoda et al, published byPergamon Press (1978).

Unfortunately, such antiviral compounds, based upon naturally occurringpyrimidinones have a serious disadvantage in that these compounds arerapidly metabolized, generally having a metabolic half life of less than30 minutes. Such short metabolic life has not permitted such compoundsto be effectively used under In Vivo conditions.

Certain compounds, based upon 4-Deoxo uracil have recently beensynthesized by two of the inventors herein and presented in a thesis byAlan Curtis Schroeder in 1978. Such thesis does not in general discussor suggest any anti-viral activity by 5 substituted 4-Deoxo uracilcompounds except on page 98 of the thesis wherein it was indicated thatsuch compounds would be tested against Herpes Virus in mouse L cells.There was no indication that such compounds would in fact have anyeffect after such tests.

BRIEF DESCRIPTION OF THE INVENTION

In accordance with the invention, there is provided a method forinhibiting the replication of the DNA virus which induces formation ofthymidine kinase enzyme. In accordance with the method, the virus isexposed to an effective concentration of the compound of the formula:##STR1## wherein R₁ is a radical selected from the group consisting ofhalogen, --SCH₃, --OH, alkoxy, cyano, methylamino, carboxy, formyl,nitro and unsubstituted or halosubstituted hydrocarbon groups of 1through 3 carbn atoms; R₂ is hydrogen; halogen or hydroxy; and R₃ ishydroxy, --OP(O)8oh9₂, amino, or --OCOR₄ where R₄ is lower alkyl of 1through 6 carbon atoms.

In furtherance of the invention, anti-viral compounds are provided whichinclude those where R₁ of the above formula is a radical selected fromthe group of chloro, iodo, hydroxy, alkoxyalkyl, hydroxyalkyl,methylamino, formyl, nitro, unsubstituted hydrocarbon groups of 2 toabout 3 carbon atoms or halosubstituted hydrocarbon groups of 1 to about3 carbon atoms; R₂ is hydrogen or hydroxy, and R₃ is hydroxy,--OP(O)(OH)₂, amino or --OCOR₄ where R₄ is alkyl, alkenyl or alkoxyalkylof 2 to about 18 carbon atoms.

DETAILED DESCRIPTION OF THE INVENTION

As previously discussed, the method of the invention comprisesinhibiting the replication of a DNA virus which induces formation ofthymidine kinase enzyme, by exposing the virus to an effectiveconcentration of a compound of the formula: ##STR2## In accordance withthe methods of the invention, R₁ of the formula is a radical selectedfrom the group consisting of halogen, --SCH₃, --OH, alkoxy, cyano,methylamino, carboxy, formyl, nitro and unsubstituted or halosubstitutedhydrocarbon groups of 1 through 3 carbon atoms. The most preferred R₁groups are halogen, alkyl, haloalkyl, alkenyl, haloalkenyl, alkynyl orhaloalkynyl groups. Particular compounds which will have goodeffectiveness are those compounds wherein R₁ is selected from methyl,ethynyl, ethyl, propyl, propyny, iodo and bromo groups. Such compoundshave been unexpectedly found to have superior effectiveness over thosecompounds wherein R₁ is an iodo or ethynyl group.

As previously discussed, R₂ is hydrogen; halogen or hydroxy but ispreferably hydrogen, fluorine or hydroxy. R₃, as previously discussed ishydroxy, --OP(O)(OH)₂, amino or --OCOR₄ where R₄ is lower alkyl of 1through 6 carbon atoms. Preferably, R₃ is hydroxy. Compounds wherein R₃is OP(O)(OH)₂, amino or --OCOR₄, as previously discussed, are generallyin themselves, not effective but in In Vivo environments are rapidlyconverted to compounds wherein R₃ is hydroxy which then undergo furthermetabolic activation.

As indicated above in connection with the compounds of the presentinvention R₁ includes various radicals like alkoxyalkyl andhydroxyalkyl. Specific representative examples include, but are notlimited to, methoxymethyl, methoxyethyl, hydroxymethyl, and2-hydroxypropyl. In addition to these radicals the compounds asdisclosed hereinabove include unsubstituted hydrocarbon groups of 2 toabout 3 carbon atoms or halosubstituted hydrocarbons having from 1 toabout 3 carbon atoms. Typical preferred examples of such groups includeethyl, propyl, ethynyl, propynyl, and bromo-vinyl, to name but a few.

Besides hydroxy and --OP(O)(OH)₂ groups for R₃, the compounds of thepresent invention include esters designated by OCOR₄. R₄ may be analkyl, alkenyl or an alkoxyalkyl radical having from 2 to about 18carbon atoms, and include, for example, preferred members like butyl,undecyl and heptadecenyl and their isomers, such as iso-butyl,sec.-butyl, and t-butyl.

Examples of compounds suitable for use in accordance with the inventionare:

1. 1-(2-Deoxy-β-D-ribofuranosyl)-5-(methylmercapto)-2-pyrimidinone

2. 1-(2-Deoxy-β-D-ribofuranosyl)-5-(methyl)-2-pyrimidinone

3. 1-(2-Deoxy-β-D-ribofuranosyl)-5-(iodo)-2-pyrimidinone

4. 1-(2-Deoxy-β-D-ribofuranosyl)-5-(bromo)-2-pyrimidinone

5. 1-(2-Deoxy-β-D-ribofuranosyl)-5-(trifluoromethyl)-2-pyrimidinone

6. 1-(2-Deoxy-β-D-ribofuranosyl)-5-(nitro)-2-pyrimidinone

7. 1-(2-Deoxy-β-D-ribofuranosyl)-5-(cyano)-2-pyrimidinone

8. 1-(2-Deoxy-β-D-ribofuranosyl)-5-(ethynyl)-2-pyrimidinone

9. 1-(2-Dexoyβ-D-ribofuranosyl)-5-(propynyl)-2-pyrimidinone

10. 1-(2-Deoxy-β-D-ribofuranosyl)-5-(propyl)-2-pyrimidinone

11. 1-(2-Deoxy-β-D-ribofuranosyl)-5-(bromo-vinyl)-2-pyrimidinone

12. 1-(2-Deoxy-β-D-ribofuranosyl)-5-(formyl)-2-pyrimidinone

13. 1-(2-Deoxy, 2-fluoro-β-D-arabinofuranosyl)-5-(methyl)-2-pyrimidinone

14. 1-(β-D-arabinofuranosyl)-5-(methyl)-2-pyrimidinone

Two especially effective compounds for use in accordance with thepresent invention is the compound wherein R₁ is iodo or ethynyl; R₂ ishydrogen and R₃ is hydroxy.

The preferred deoxyriboside of the present invention is where R₁ isiodo. This particular compound has a high level of anti-viral activity,particularly against herpes virus group and a low level of toxicity forthe host cell. In relation to the1-(2-Deoxy-β-D-ribofuranosyl)-5-(iodo)-2-pyrimidinone, Oftebro et al.,Biochemical Pharmacology, Vol. 21, Pergamon Press (1972) pp. 2451-2456and Oyen et al., Biochim Biophys. Acta, 182 (1969) pp. 567-569 eachdisclose the 5-fluoro derivative of1-(2-Deoxy-β-D-ribofuranosyl)-2-pyrimidinone. Although exhibitinganti-viral activity, the structurally related fluoro substitutedanalogue was found to be more toxic to the host cell than to the virus,and therefore, was found not to have any potential value as ananti-viral agent against HSV-2. Accordingly, the5-iodo-pyrimidin-2-one-deoxyriboside and its combined properties wereindeed an important and surprising discovery.

Another 5-iodo deoxyriboside has been successfully used in treatingHerpes virus. Torrence et al., Frontiers in Bioorganic Chemistry AndMolecular Biology, Elsevier/North-Holland, Biomedical Press (1979) pp.59-85 disclose 5-iodo-2'-deoxyuridine widely known by the generic nameidoxuridine. Although known to be useful against Herpes virus,idoxuridine is rapidly inactivated by nucleotidases upon systemicadministration to a host species. After intravenous injection, most ofthe active form of the drug disappears from the blood in about thirtyminutes. In addition, it has been reported that the systemicadministration of idoxuridine may produce toxicities, such as bonemarrow depression. Consequently, therapeutic use of idoxuridine islimited almost exclusively to topical administration. At present,idoxuridine is limited to topical treatment of herpes simplex keratitesof the eye. It has been reported that herpatic lesions of the skin donot respond. Hence, idoxuridine has very limited applications even whenemployed topically. In contradistinction,5-iodo-pyrimidin-2-one-deoxyriboside of the present invention can beused against HSV-2 and can be administered orally, intraperitoneally orsubcutaneously without significant toxicity to the host or loss ofactivity as demonstrated by Example 9 below.

5-halo-pyrimidin-2-one ribosides have been reported in the literature.For example, East German Patent 134,429 (1979) discloses a singlecompound, namely 5-fluoro-pyrimidin-2-one riboside as possessinganti-viral activity. However, as pointed out above, the more closelystructurally related 5-fluoro deoxyriboside was found to possessanti-viral activity, but was more toxic to the host than to the virus asdemonstrated in Example 8 below.

McCormick et al., Biochemical Pharmacology, Vol. 29 (1980) pp. 830-832reported on the 5-fluoro, 5-chloro and 5-bromo derivatives ofpyrimidine-2-one 1-β-D-ribofuranosyl. McCormick et al. reported that the5-fluoro and 5-bromo derivatives show similar activities as inhibitorsof the enzyme cytidine deaminase. But, when tested for anti-tumoractivity against murine leukemia L 1210 only the 5-fluoro was active.Hence, while McCormick et al. seem to show similarities in activitybetween fluoro, chloro and bromo derivatives of 1-β-D-ribofuranosyl inthe inhibition of cytidine deaminase the lack of anti-tumor activity forthe 5-chloro and 5-bromo substituted compounds fail to support theconclusion that the halogens are interchangeable in this compound.McCormick et al. also failed to teach anti-viral activity or the 5-iodohomalog. The disclosure of cytidine deaminase inhibition or the limitedanti-tumor activity of the 5-fluoro riboside is not viewed as asuggestion of possible anti-viral activity with respect to the5-iodo-pyrimidine-2-one-deoxyriboside.

In general, such compounds are prepared by reacting a compound of theformula: ##STR3## with a substituted sugar of the formula: ##STR4##wherein R_(a), R_(b) and R_(c) are radicals which are non-reactiveduring the reaction of I with II and which can be converted to thedesired R₂, R₃ and H respectively after reaction of I with II. Detaileddiscussions of how compounds for use in accordance with the method ofthe present invention can be prepared are found in Synthesis andAntiviral Activity of1-(2-Deoxy-β-D-ribofuranosyl)-5-(methylmercapto)-2-pyrimidinone bySchroeder et al published in the Journal of Medicinal Chemistry, Volume24, No. 1, pages 109-112, available to the public Jan. 5, 1981. Furtherdiscussion of methods of synthesis of compounds for use in accordancewith the method of the present invention is made by Wightman et al.,Collection of Czechoslavakian Chemical Communications, Volume 38,beginning at page 1381 (1973) and "Synthesis of New Nucleoside AnalosDerived from 4-Deoxo uracil and 6-substituted Uracils" by Schroederdissertation at the State University of New York at Buffalo (1978).

In accordance with the method of the invention, the replication ofnumerous viruses can be inhibited. In particular, viruses which inducethe formation of thymidine kinase enzyme are inhibited in accordancewith the method of the invention. Such viruses generally includeessentially all Herpes type viruses including Herpes simplex type 1,Herpes simplex type 2, varicella coster, Epstein-bar virus, Cytomegalovirus, varicella zoster, Herpes zoster and variolla. It is known thatsuch viruses cause numerous infections in man including localizedinfections such as infections of the eye and genitals.

The following examples serve to illustrate and not limit the presentinvention.

EXAMPLE 1 1-(2-Deoxy-β-D-Ribofuranosyl)-5-Ethynyl-2-Pyrimidinone

A suspension of 15.06 g (67.83 mmol) of 5-iodo-2(1H)-pyrimidinone wasrefluxed in 40 ml of hexamethyldisilazane and 2 ml ofchlorotrimethylsilane for 1 hour. The excess reagent was removed invacuo to yield a yellow oil 5-iodo-2-trimethylsilyloxypyrimidine, whichwas dissolved with 30 ml of dry degassed triethylamine. To this solutionwas added 11.5 ml (81.37 mmol) of trimethylsilylacetylene, 0.32 g (2.5mol %) of CuI and 0.48 g (1 mol %) of (φ₃ P)₂ PdCl₂. The reactionmixture was stirred under nitrogen, at room temperature, for 3 days anddiluted with 100 ml of dry THF. The mixture was filtered under drynitrogen; the precipitate washed several times with dry THF and thefiltrate was concentrated to a residue. The latter was treated withmethanol to give a white crystalline, chromatographically homogeneousmaterial 5-(2-Trimethylsilyl)ethynyl-2(1H)-pyrimidinone (9.99 g, 76.6%).Analytically pure material could be obtained by recrystallization frommethanol; mp 203°-206° C.

1.41 g (7.32 mmol) of 5-(2-trimethylsilylethynyl)-2(1H)-pyrimidinone wasrefluxed in 14 ml of hexamethyldisilazane and 0.3 ml ofchlorotrimethylsilane for 3 hours, and the resulting solution wasconcentrated to an oily residue. The residual solvent was removed byco-evaporation with 1,2-dichloroethane (2×20 ml). The residue wasdissolved in 30 ml of anhydrous dichloroethane and the solution wasadded to a cooled solution of 2.5 g (5.82 mmol) of the halogenose1-(3,5-di-O-(p-chlorobenzoyl)-2-deoxy-alpha-D-ribofuranosyl)chloride.The cooled mixture was then treated, dropwise, with a solution of 0.17ml of SnCl₄ in 25 ml of anhydrous 1,2-dichloroethane. The mixture wasstirred at 0° C. for 2 hours and periodically monitored by tlc (15%ethyl acetate in methylene chloride; Macherey-Nagel silica gel G). Themixture was diluted with dichloroethane (100 ml) and saturatedbicarbonate solution (50 ml), and filtered over Celite, the residuebeing washed several times with dichloroethane. The organic layer wassubsequently washed with water (50 ml), dried over MgSO₄, andconcentrated to a residue which was chromatographed on 100 g of silicagel (eluted with a gradient of 0 to 12% ethyl acetate in methylenechloride). The fractions containing the slower moving alpha anomer,1-(3,5-di-O-(p-chlorobenzoyl)-2-deoxy-α-D-ribofuranosyl)-5-(2-trimethylsilyl)-ethynyl-2-pyrimidinone,were pooled, concentrated to a white residue which was recrystallizedfrom ethanol to provide, after drying, 0.48 g (14.2%); mp 150°-152° C.

The faster moving beta anomer,1-(3,5-di-O-(p-chlorobenzoyl)-2-deoxy-β-D-ribofuranosyl)-5-(2-trimethylsilyl)ethynyl-2-pyrimidinone,was obtained in a similar manner to that described for the alpha anomer.After recrystallization from ethanol and drying, 0.42 g (12.4%) of thewhite powder was obtained; mp 183°-185° C.

0.31 g (0.5 mmol) of the beta anomer was then added to 20 ml of coldanhydrous methanol presaturated with dry ammonia, and the mixture, aftersealing the reaction vessel, was stirred at 4° C. for 6 hours. Theresulting solution was concentrated to an oil; the latter was treatedwith acetone and concentrated to a minimum volume with concomitantprecipitation of the product. The mixture was treated with small amountsof acetone-ether and cooled. The product,1-(2-deoxy-β-D-ribofuranosyl)-5-ethynyl-2-pyrimidinone, was collected byfiltration, washed with acetone-ether and dried to yield 69 mg (55.9%)of the off-white powder; dec above 130° C.; NMR (DMSO-d₆ +D₂ O) delta2.26 (m, 2, 2'-H), 3.68 (m, 2, 5'-H), 3.97 (m, 1, 4'-H), 4.27 (m, 2,3'-H and C-H), 6.03 (t, 1, 1'-H); J_(1'),2' =6 Hz), 8.63 (d, 1, 6-H,J₆,4 =3 Hz), 8.73 (d, 1, 4-H, H₄,6 =3 Hz); IR (KBr) Nu max 3525(shoulder), 3220 (broad), 2925 (shoulder), 2100, 1660, 1423, 1350, 1265,1110, 1070 (shoulder), 925 cm⁻¹ ; UV (MeOH) lambda max 32 nm Anal. (C₁₁H₁₂ N₂ O₄); C, H, N.

EXAMPLE 2 1-(2-Deoxy-β-D-Ribofuranosyl)-5 -(1-propynyl)-2-pyrimidinone

31.67 g (0.13 mol) of 5-iodo-2-methoxypyrimidine, 0.73 g (2.9 mol %) ofCuI and 1.02 g (1.1 mol%) of bis(triphenylphosphine)PdCl₂ were suspendedin 200 ml of anhydrous triethylamine (distilled over BaO) in Parrpressure bottle. The bottle was evacuated and filled with 85% propyne.The bottle was repeatedly shaken and filled with propyne until thepressure had stabilized at 20 psi, and then the mixture was shaken, in aParr hydrogenator, for 24 hours. More propyne was added at this timeshaking was continued for an additional 48 hours. On tlc (methylenechloride), there was only one major product; no starting material wasobserved. The mixture was diluted with methylene chloride (300 ml),washed with saturated bicarbonate solution (2×60 ml), dried overmagnesium sulfate and concentrated to a minimum volume with attendantprecipitation. Petroleum ether was added to the mixture and aftercooling, the first crop was obtained by filtration. The filtrate wasconcentrated to give a second crop. Both crops were dried and sublimedat 0.3 mm Hg (max. oil bath temp. 100° C.) to yield 15.26 g (76.7%) ofanalytically pure, white-crystalline material,2-methoxy-5-(1-propynyl)pyrimidine; mp 88°-89.5° C.).

Chlorotrimethylsilane (4.11 ml; 32.5 mmol) was introduced by syringe,into a solution of 1.5 g (10.2 mmol) of the2-methoxy-5-(1-propynyl)pyrimidine and 4.56 g (30.44 mmol) of NaI in 35ml of anhydrous acetonitrile maintained under an atmosphere of drynitrogen and removed from light. The mixture was stirred at 50° C. for21/2 hours with periodic monitoring by tlc. The mixture was cooled in anice-bath and 3.5 g (8.14 mmol) of the halogenose,1-(3,5-di-O-(p-chlorobenzoyl)-2-deoxy-α-D-ribofuranosyl)-chloride werethen added. To this mixture was added 3 ml of 1N trimethylsilyl triflatein 1,2-dichloroethane; the mixture was stirred at 0° C. for 1 hour andthen at room temperature for 21/2 hours. The reaction mixture was thendiluted with dichloromethane (150 ml) and saturated aqueous bicarbonate(65 ml). The organic extract was subsequently washed with water (60 ml),dried over magnesium sulfate and concentrated to a residue which wassubjected to flash chromatography on 80 g of silica gel. The fractionscontaining the slower moving alpha anomer were pooled and concentratedto a minimum volume with attendant precipitation. The mixture was cooledand filtered; the white product washed with diethyl ether and dried at50° C. to provide 1.1 g (25.7%) of1-(3,5-di-O-)p-chlorobenzoyl)-2-deoxy-α-D-ribofuranosyl)-5-(1-propynyl)-2-pyrimidinone;mp 176°-178° C.

The fractions containing the faster moving beta anomer1-(3,5-di-O-(p-chlorobenzoyl)-2-deoxy-β-D-ribofuranosyl)-5-(1-propynyl)-2-pyrimidinonewere pooled and concentrated to yield a foam which was subsequentlydried.

300 mg (0.57 mmol) of the beta anomer was added to a cold, anhydrous,saturated solution of methanolic ammonia (15 ml), and the flask wassealed. The mixture was stirred at 4° C. for 4 hours. Tlc (10% MeOH/CH₂Cl₂) showed several minor fluorescent products. The solution wasconcentrated, in vacuo, to an oil which was chromatographed on 20×20 cmsilica gel plates (10% MeOH/CH₂ Cl₂). The major fluorescent band wasextracted with a solution of 20% methanol in methylene chloride and theextract was concentrated to a syrup. The latter was dried to give1-(2-deoxy-β-D-ribofuranosyl)-5-(1-propynyl)-2-pyrimidinone as a paleyellow, chromatographically homogeneous foam (82 mg; 57.7%); NMR(DMSO-d₆ +D₂ O) delta 1.18 (t, ethanol, H₂ O), 1.83-2.67 (m, 5, H'-2 and--C.tbd.CH₃), 3.3-4.5 (ethanol, H₂ O and sugar protons), 6.08 (t, 1,H'-1, J_(1'),2' =6 Hz), 7.97 (dd, 2. H-4 and H-6; J₄,6 =3 Hz); IR (KBr)Nu max 3350 (broad), 2920 (shoulder), 2600 (shoulder), 1650, 1500, 1250,1090 cm⁻¹ ; Anal. (C₁₂ H₁₄ N₂ O₄.0.4H₂ O) C, H, N,

EXAMPLE 3 1-(2-Deoxy-β-D-Ribofuranosyl)-5-iodo-2-pyrimidinone

2-Pyrimidinone (6 g, 62.44 mmol) and N-iodosuccinimide (14.7 g, 65.3mmol) in dry DMF (30 ml) were stirred for 48 hours at room temperaturewith the exclusion of both light and moisture. The mixture was added toether (50 ml) with stirring and the supernatant was decanted. Theprecipitate was collected by filtration, repeatedly washed with acetoneand finally with methanol, until the filtrate became light yellow. Afterdrying in vacuo the yellow granular product, 5-iodo-2(1H)-pyrimidinone,appeared to be pure by tlc and spectra, but the elemental analysisindicated that it was contaminated with a trace amount of DMF. Yield:11.35 g (77.5%).

A suspension of 0.86 g (3.87 mmol) of the 5-iodo-2(1H)-pyrimidinone in15 ml of hexamethyldisilazane and 0.3 ml of chlorotrimethylsilane wasrefluxed for 2 hours (with the exclusion of moisture), cooled andconcentrated in vacuo to yield a yellow oil. Residual solvent wasremoved by coevaporation with 1,2-dichloroethane (2×10 ml). 1.65 g (3.84mmol) of the sugar halide1-(3,5-di-O-(p-chlorobenzoyl)-2-(deoxy-α-D-ribofuranosyl) chloride, wereadded to the oil; the mixture was dissolved in 50 ml of anhydrous1,2-dichloroethane and cooled in an ice bath. To the cooled solution wasadded, dropwise, a solution of 0.2 ml (1.7 mmol) of SnCl₄ in 25 ml ofanhydrous dichloroethane. The reaction mixture was stirred at 0° C. for21/2 hours at which time tlc (17% ethyl acetate in dichloroethane)showed disappearance of the starting material, indicating that thereaction was essentially complete. The mixtur was diluted with 60 ml ofdichloroethane and 50 ml of saturated bicarbonate, and the resultingemulsion was filtered over Celite, the precipitate being washed severaltimes with 1,2-dichloroethane. The organic layer was washed with 50 mlof water, dried over anhydrous magnesium sulfate and concentrated to aresidue which on tlc showed two major spots of equal intensity (R_(f)values 0.19 for the alpha anomer,1-[3,5-di-O-(p-chlorobenzoyl)-2-deoxy-α-D-ribofuranosyl]-5-iodo-2-pyrimidinone,and 0.3 for the beta anomer1-[3,5-di-O-(p-chlorobenzoyl)-2-deoxy-β-D-ribofuranosyl]-5-iodo-2-pyrimidinone;17% ethyl acetate dichloroethane; Macherey-Nagel silica gel G). Thisresidue was chromatographed on 90 g of silica el and eluted with agradient of 0 to 25% ethyl acetate in dichloroethane. The fractions,containing the slower moving alpha anomer were pooled, concentrated to aresidue which weighed, after drying, 0.48 g (20.4%). The whitecrystalline compound was obtained by recrystallization fromethanol-acetone; mp 175°-176° C.; [alpha]_(D) ²⁶ ==20.03° (CHCl₃,c.0.108); NMR (CDCl₃) dela 2.8 (m, 2, 2'-H), 4.6 (d, 2, 5═-H), 5.0 (t,1, 4'-H), 5.65 (d, 1, 3'-H), 6.27 (d, 1, 1'-H, J_(1'),2' =7 Hz),7.25-8.12 (m, 8, phenyl), 8.18 (d, 1, 6-H, J₆,4 =3 Hz), 8.68 (d, 1, 4-H,J₄,6 =3 Hz); IR (CHCl₃ Nu max 3000, 1725, 1665, 1595, 1490, 1380, 1260,1090, 1010 cm⁻¹ ; UV (CHCl₃)lambda max (epsilon max) 340 nm (3600).Anal. (C₂₃ H₁₇ Cl₂ IN₂ O₆) C, H, Cl, I, N.

The faster moving beta anomer was obtained in the same manner describedfor the alpha anomer to yield 0.46 g (19.5%) of1-(3,5-di-O-(p-chlorobenzoyl)-2-deoxy-β-D-ribofuranosyl)-5-iodo-2-pyrimidinone;mp 136°-138° C.; [alpha]_(D) ²⁶ =-13.66α (CHCl₃, c 0.10); 'H NMR (CDCl₃)delta 2.32 (m, 1, 2'-H) 3.2 (m, 1, 2'-H), 4.75 (m, 3, 4'-H, and 5'-H),5.62 (d, 1, 3'-H), 6.27 (t, 1, 1'-H, J_(1'),2' =7 Hz), 7.30-8.17 (m, 8,aromatic), 8.27 (d, 1, 6-H, J₆,4 =3 Hz), 8.57 (d, 1, 4-H, J₄,6 =3 Hz);IR (CHCl₃) Nu max 3000, 175, 1675, 1595, 1500, 1380, 1260, 1090, 1010cm⁻¹ ; UV (CHCl₃) lambda max (epsilon max) 341 nm (3500). Anal. (C₂₃ H₁₇Cl₂ IN₂ O₆) C, H, Cl, I, N.

0.41 g (0.67 mmol) of the beta anomer was added to a cold anhydroussolution of methanolic ammonia (25 ml); the flask was scaled and themixture was stirred at 4° C. for 5 hours. The reaction was complete asindicated by tlc (10% MeOH/CH₂ Cl₂). The solution was concentrated to asyrup which was subsequently treated with acetone and chilled (-20° C.)to give, after several days, the crystalline material1-(2-deoxy-β-D-ribofuranosyl)-5-iodo-2-pyrimidinone. The product wascollected by filtration, washed with acetone and dried, to provide 100mg (45.1%) of the pale yellow material, 160°-170° C. (decomposes). 'HNMR (DMSO-d₆) delta 2.35 (m,. 2, 2'-H), 3.65 (m, 2, 5'-H), 3.90 (m, 1,4'-H), 4.22 (m, 1, 3'-H), 5.22 (t, 2, OH), 6.0 (t, 1, 1'-H); J_(1'),2' =6 Hz), 8.62 (d, 1, 6-H, J₆,4 =3 Hz), 8.75 (d, 1, 4-H). IR (KBr) Nu max3390, 3140, (broad), 2925, 1640, 1600 (shoulder), 1500, 1390, 1290,1250, 1100, 1070 cm⁻¹ ; UV (MeOH) lambda max (epsilon max) 335 nm(2830). Anal. (C₉ H₁₁ IN₂ O₄) C, H, I, N.

EXAMPLE 4

The substituted pyrimidinone of Example 3,1-(2-deoxy)-β-D-ribofuranosyl)-5-iodo-2-pyrimidinone (IPdR) was testedin vivo. Three groups of five Swiss Webster Balb/C mice weighing from 19to 23 grams were implanted with HSV-2 (333 strain) with a virus load of5×10⁵ plaque forming units.

Drug administration began one day following virus implant. The IPdR wasadministered subcutaneously to a first group of mice andintraperitoneally to a second group of mice. The third group of micewhich performed as controls were not given any IPdR. The dosage of IPdRwas at the rate of 100 mg/kg twice daily for 2.5 days for a total of 5doses. The results are provided in Table 1 below:

                  TABLE 1                                                         ______________________________________                                        GROUP       DAYS--SURVIVAL                                                    ______________________________________                                        Control     5 out of 5 died (9.4 days average)                                Subcutaneous                                                                              1 died on day 11; 2 died on day 13                                IPdR        (12 days average) 2 long term survivors*                          Intraperitoneal                                                                           1 died on day 17                                                  IPdR        4 long term survivors*                                            ______________________________________                                         *>30 days                                                                

EXAMPLE 5

In accordance with the present invention,1-(2-Deoxy-β-D-ribofuranosyl)-5-(methylmercapto)-2-pyrimidinone isprepared essentially in accordance with the procedure set forth in"Snythesis and Antiviral Activity of1-(2-Deoxy-β-D-ribofuranosyl)-5-(methylmercapto)-2-pyrimidinone" bySchroeder and Bardos and Cheng, Volume 24, page 109, January 1981. HeLacells were infected in 1640 RPMI medium with herpes simplex type 1(HSV-1) and independently with herpes simplex type 2 (HSV-2) virus at amultiplicity of 5 to 10 plaque forming units per cell. The compositionof 1640 RPMI medium is reported in "Biological Activity of 5 Ethyl, 5Propyl, and 5 Vinyl 2'-Deoxyuridine" by Cheng et al published inAntimicrobial Agents and Chemotherapy, Volume 10, beginning at page 119(1976). 1640 RPMI medium is commercially available from Gibco Company,Grand Island, N.Y. After 1 hour, virus absorption, the drugs were added.Resulting cultures were analyzed for virus titer at 24 hours postinfection a described in the procedure set forth in "Biological Activityof 5-Ethyl, 5-Propyl and 5-Vinyl 2'-uridine" by Cheng et al. The resultsare set forth in Table 2. The numbers set forth in Table 2 show thenumber of plaque forming units in the control which contained nomethylmercapto compound and the number of units at concentrations of100, 200 and 400 micromoles of the methylmercapto compound. The resultsclearly indicate substantial decrease in the number of plaque formingunits in the presence of1-(2-Deoxy-β-D-ribofuranosyl)-5-(methylmercapto)-2-pyrimidinone.

                  TABLE 2                                                         ______________________________________                                        compound      plaque-forming units/mL                                         conc., μM  HSV-1(Kos) HSV-2 (333)                                          ______________________________________                                        0             1.5 × 10.sup.7                                                                     1.2 × 10.sup.7                                 100           6.4 × 10.sup.7                                                                     1.3 × 10.sup.7                                 200           1.7 × 10.sup.6                                                                     3.1 × 10.sup.6                                 400           3.4 × 10.sup.5                                                                     3.2 × 10.sup.5                                 ______________________________________                                    

EXAMPLE 6

The methylmercapto composition, as described in Example 5. was testedfor binding affinity with thymidine kinase from various sources. Viruseswhich induce the production of thymidine kinase, induce thymidine kinasespecific to the virus. Tests of the binding affinity of themethylmercapto compound with thymidine kinase extracted from human cellsshowed little binding affinity; whereas, the binding affinity of themethylmercapto compound with thymidine kinase extracted from cellsinfected with herpes simplex 1 virus and with Varicella zoster virusinfected cells, showed great binding affinity. It is believed that thecompound of the invention, in order to become active in inhibiting thereplication of the virus, must become phosphorylated. For suchphosphorylation to occur, the thymidine kinase must first bind to thecompound. Since binding with thymidine kinase produced by the virus ismuch more efficient and effective than binding with thymidine kinasefrom other sources, phosphorylation of the compound occurs more rapidlyin the presence of active viruses producing thymidine kinase. Thecompound, activated by phosphorylation, then is able to interfere withreplication of the virus.

EXAMPLE 7

1-(2-Deoxy-α-D-ribofuranosyl)-5-(methyl)-2-pyrimidinone, also known as4-Deoxothymidine, was prepared by thonation of the 4-oxo group ofdiacetylated thymidine with phosphorus pentasulfide, followed bydesulfuration of the 4-thiothymidine derivative by Raney nickelreduction. The method for preparation of the above described methylcompound is essentially the same as described by Wightman et al. inCollection of Czechoslavakian Chemical Communications, Volume 38,beginning at page 1381 (1973).

The above described methyl compound was tested for viral inhibitionsubstantially in accordance with the method of Example 5 except that theconcentrations were 50 and 100 micromolar. The methyl compound showed a95.5% inhibition for HSV-1 at 50 micromoles when compared with anuntreated control and an 87.9% inhibition for HSV-2 when compared withan untreated control. By comparison, methylmercapto compounds of Example5 at the same 50 micromolar concentration showed only a 41.1% inhibitionfor HSV-1 virus and a 57.2% inhibition for HSV-2 virus. At 100micromolar concentration, a 99% inhibition was shown for the methylcompound for HSV-1 virus and a 98.3% inhibition was shown for HSV-2virus. Again, by comparison, the merthylmercapto compound of Example 5only showed a 83.8% inhibition for HSV-1 and a 79.3% inhibition forHSV-2.

EXAMPLE 8

Part A--Antiviral Activity

The effects of 1-(2-Deoxy-β-D-ribofuranosyl)-5-iodo-2-pyrimidinone(IPdR) of Example 3 were compared with1-(2-Deoxy-β-D-ribofuranosyl)-5-fluoro-2-pyrimidinone (FPdR) on HSV-2(strain 333) in Hela cells. Twenty four well plates (sterile) wereplated with 10⁶ Vero cells/well the day before infecting. 250 PFU ofHSV-2 were used in each well. The test compounds, IPdR and FPdR, wereadded at zero times of post infection and the cultures incubated at 37°C. for 48 hours. At the end of the incubation period the media wasremoved from Vero cells. Plates were strained with 0.8% crystal violetin 50% ethanol for 15 minutes. The plaque was counted. Table 3, below,provides the results.

                  TABLE 3                                                         ______________________________________                                        ANTIVIRAL ACTIVITY                                                            Concentration (μM)                                                                          Plaque Reduction (%)                                         of Compound      IPdR     FPdR                                                ______________________________________                                        100              51.1     50.5                                                ______________________________________                                    

Part B--Cytotoxicity

To compare the toxicity of FPdR and IPdR human nasopharyngeal carcinomaKB cells obtained from the American Type Culture Collection weremaintained as a monolayer in RPMI 1640 supplemented with 5% fetal bovineserum, 10 mM HEPES buffer (pH 7.4) and karamycin (100 μg/ml). Cells weremaintained at 37° C. in a humidified atmosphere of 5% CO₂ in air. Cellnumbers were determined with an electronic particle counter (ParticleData, Inc., Elmhurst, Ill.).

For determination of drug effect on cell proliferation, cells wereharvested from rapidly proliferting cultures by treatment withpancreation. Cell number was determined and plated in 24 well (6 mm welldiameter) plates at a concentratin of 5×10³ cells/ml. Drug exposureswere initiated by a complete change of medium after overnightincubation. Following a 72 hour drug exposure 50 ml. of thiazolyl bluewas added and incubated for a further 4 hour period. The media from theplates was aspirated completely and 250 ml DMSO was added to each well.The plates were placed on a shaker for 5 minutes and the blue solutiontransferred to 96 well plates and read at 540 nm with a scanningmultiwell spectrophotometer (Biotek Instruments, Inc. Burlington, Vt.).Table 4, below, provides the relevant test data.

                  TABLE 4                                                         ______________________________________                                        CYTOTOXICITY                                                                  Compound   Concentrtion (μm) % Growth                                                                    ID.sub.50                                       ______________________________________                                        FPdR       1.0/102            25 μm                                                   10/84                                                                         25/49                                                                         50/21                                                              IPdR       100/75             >200 μm                                                 200/80                                                             ______________________________________                                    

The foregoing comparative test data shows that IPdR and FPdR arecomparable in antiviral activity. However, Part B demonstrates that FPdRhas a toxicity against the host cells which is significantly greaterthan IPdR. Accordingly, this data provides evidence that notwithstandingthe equivalent antiviral activity of FPdR and IPdR the high level oftoxicity of the 5-fluoro homologue renders it ineffective as atherapeutic agent.

EXAMPLE 9

In order to examine the activity of IPdR administered by various routes,i.e., oral, intraperitoneal (IP) and subcutaneous (SC), 6 to 8 week oldSwiss-Webster female mice (Hilltop Laboratories, Chatsworth, Calif.weighing approximately 20 g were infected intraperitoneally on day 0with 5×10⁵ PFU of HSV-2 2 (Strain 333). The drugs were administered oncea day for five days or twice daily (12 hour intervals) for 2.5 daysbeginning 24 hours postinfection. Mean body weight determinations ofdrug treated and control animals were made during the treatment periodas an indicator of sublethal toxicity. Deaths were recorded through day45. Table 5, below, summarizes the results.

                                      TABLE 5                                     __________________________________________________________________________    ANTIVIRAL ACTIVITY .OF IPdR IN MICE                                           Drug               Survivors/                                                                           Mean Survival                                       (mg/kg)                                                                              Route                                                                              Schedule.sup.a                                                                       Total  Time.sup.b (days)                                                                     % ILS.sup.c                                 __________________________________________________________________________    Control                                                                              IP   1 × 5                                                                          1/10 (10).sup.d                                                                      9.6 ± 1.1.sup.e                                                                    --                                          EPdR (100)                                                                           IP   1 × 5                                                                          1/5 (20)                                                                             9.0 ± 0.8                                                                          94                                          IPdR (100)                                                                           IP   1 × 5                                                                          7/10 (70)                                                                            12.0 ± 4.4                                                                         129                                         Control                                                                              SC   1 × 5                                                                          0/5 (0)                                                                              9.4 ± 1.1                                                                          --                                          IPdR (100)                                                                           SC   1 × 5                                                                          2/5 (40)                                                                             12.3 ± 1.2                                                                         131                                         Control                                                                              IP   2 × 21/2                                                                       0/10 (0)                                                                             9.3 ± 1.1                                                                          --                                          IPdR (10)                                                                            IP   2 × 21/2                                                                       0/5 (0)                                                                              12.8 ± 3.6                                                                         133                                         IPdR (40)                                                                            IP   2 × 21/2                                                                       2/5 (40)                                                                             10.0 ± 1.0                                                                         108                                         IPdR (100)                                                                           IP   2 × 21/2                                                                       6/10 (60)                                                                            12.5 ± 1.3                                                                         135                                         Control                                                                              oral 2 × 21/2                                                                       4/20 (20)                                                                            10.6 ± 2.1                                                                         --                                          IPdR (10)                                                                            oral 2 × 21/2                                                                       0/5 (0)                                                                              12.8 ± 3.6                                                                         123                                         IPdR (40)                                                                            oral 2 × 21/2                                                                       2/5 (40)                                                                             10.0 ± 1.0                                                                         94                                          IPdR (100)                                                                           oral 2 × 21/2                                                                       20/20 (100)                                                                          >45                                                 DHPG.sup.h (40)                                                                      oral 2 × 21/2                                                                       20/20 (100)                                                                          >45                                                 Control.sup.f                                                                        oral 2 × 21/2                                                                       0/5 (0)                                                                              10.0 ± 1.2                                                                         --                                          IPdR (100)                                                                           oral 2 × 21/2                                                                       4/5 (80)                                                                             14.0    140                                         DHPG (40)                                                                            oral 2 × 21/2                                                                       2/5 (40)                                                                             20.0 ± 7.0                                                                         200                                         Control                                                                              oral 2 × 21/2.sup.g                                                                 0/5 (0)                                                                              9.8 ± 1.3                                                                          --                                          IPdR (100)                                                                           oral 2 × 21/2                                                                       5/5 (100)                                                                            >45                                                 DHPG (40)                                                                            oral 2 × 21/2                                                                       5/5 (100)                                                                            >45                                                 __________________________________________________________________________     .sup.a daily doses × days                                               .sup.b of the mice that died                                                  .sup.c mean life span of treated mice greater than mean life span of          untreated mice in percent, excluding 45 day survivors.                        .sup.d percent survival                                                       .sup.e standard deviation                                                     .sup.f innoculation dose at 1 × 10.sup.6 PFU                            .sup.g 72 hours after implant                                                 .sup.h Dihydroxy propoxymethyl guanine   Table 5 provides further evidenc     that IPdR is active against HSV-2 in vivo. Most importantly, the potent     antiviral activity of IPdR can be maintained when given orally. However,     regardless of the route of administration IPdR can significantly increase     the life span of the host infected with HSV-2. Also, the same potent     antiviral effect of IPdR can be seen whether the drug is administered to     the animals at the onset of the HSV infection or well after initiation of     HSV-2 infection.

EXAMPLE 10

IPdR and 5-bromo-2-pyrimidinone-2-deoxyribonucleoside (BrPdR) weretested for antiherpes activity according to procedures described byCheng, Y.-C., et al. Antimicrob. Agents Chemother (1976) 10, 119. Table6, below, summarizes the results.

                  TABLE 6                                                         ______________________________________                                        Antiherpes Activities of                                                      (2-Deoxy-β-D-ribofuranosyl)-5-bromo- and -5-iodo-2-pyrimidinone                    plaque-forming units as % of control                                            BrPdR (5a)                                                                              IPdR (5b) BVdU   ACG                                    virus       (100 μM)                                                                             (100 μM)                                                                             (30 μM)                                                                           (5 μM)                              ______________________________________                                        HSV-1 (KOS) 0.6       0.27      0.1    6.5                                    HSV-1 (CLl0l)         1.6       0.4    4                                      HSV-2 (333) 4.5       2.8       1.7                                           HSV-2 (CEU-G)                                                                             7.1       9.3                                                     ACG.sup.1 (S1)        22        3.7    100                                    ACG.sup.1 (Tr7)       2.6       0.8    85                                     BVdU.sup.2            14        52     0.7                                    PFA (phosphono-       0.1              100                                    formic acid)                                                                  ______________________________________                                         .sup.1 acyclovir resistant strain of HSV1                                     .sup.2 (bromovinyl) deoxyuridine                                         

Test results showed that both BrPdR and IPdR have significant antiherpesactivities against various strains or HSV-1 and HSV-2, the latter (IPdR)showing the higher activity. IPdR also has been shown to have strongerbinding to the virus-specific thymadine kinase. IPdR was, in addition,tested and found to exhibit somewhat reduced but still significantactivity against acyclovir (ACG) and BVdU resistant strains of HSV-1 inwhich the resistance was due to modification of the thymadine kinase.The more highly ACG-resistant strain (S1) showed more cross resistancetowards IPdR than the one with a lower level of ACG resistance (Tr7).But, it is of interest that IPdR was still effective against the virusstrain resistant to acyclovir, the foremost currently used antiherpesagent. Against PFA-resistant strains (modification in the DNApolymerase), IPdR retained full activity.

We claim:
 1. 1-(2-Deoxy-β-D-ribofuranosyl)-5-(iodo)-2-pyrimidinone.